The present invention relates to an antenna and more specifically a small antenna for equipping a portable receiver.
The term small antenna is understood to mean an antenna, whose size is well below that of the wavelength of the waves received.
This type of receiver is more particularly used in systems for the transmission of radio signals from a basic transmitter and which are intended for users, carrying portable receivers, moving about within a perimeter defined by a radius of limited size around their telephone or radio telephone. These systems are more particularly known as unilateral call systems or as "Eurosignal" systems. In such systems it is desirable for the user's comfort to reduce the size of the receiver and the antenna incorporated therein to the greatest possible extent.
The antenna conventionally comprises two metal plates forming an electric dipole between which is placed the receiver. A matching circuit generally formed by an inductor is located between the receiver and each of the metal plates forming the dipole.
Efforts at reducing the overall dimensions have hitherto been mainly directed at reducing the volume occupied by the receiver and have been greatly helped by the contributions made by microelectronics in this field.
However, without changing the antenna structure it was difficult to envisage reducing the volume occupied by it.
Due to the fact that it complies with experience gained in the field of antennas and on the basis of repeated satisfactory use, it seemed difficult to cast doubts on the hitherto used antenna structure.
However, the present invention is directed at a novel antenna structure having reduced overall dimensions compared with the hitherto used antenna.